The results of identification of bacteria from positive blood cultures using MALDI-TOF mass spectrometry

Clinical Microbiology and Antimicrobial Chemotherapy. 2018; 20(4):381-386

Type
Journal article

Objective.

To evaluate the results of accelerated identification of microorganisms isolated from positive hemocultures obtained from patients of various departments of a large multi-profile hospital by MALDI-TOF MS and to compare them with classical cultural methods.

Materials and Methods.

In the period from 2017 to 2018, the study included 109 positive blood cultures from 73 patients from UIA GKB number 40 at the age of 1 to 83 years. Blood samples were taken in aseptic conditions from 2 peripheral veins according to the standard protocol in 12 departments of the health facility. Identification of the grown up colonies was carried out by 2 methods: phenotypic (using the automatic bacteriological analyzer Vitek 2 (BioMerieux, France), biochemical tests, Gram stain, catalase test, oxidase, latex agglutination) in the laboratory of microbiology and MALDI-TOF MS on the Vitek MS analyzer (BioMerieux, France) in the QualityMed laboratory. The transportation of blood from the health facility to the laboratory was carried out with the help of a courier, the delivery time varied from 7 hours to 2 days. Polymicrobial hemocultures (4 vials), cases of fungemia (4 vials), and also 1 vial because of late delivery times are excluded from the study.

Results.

In total, out of 100 vials included in the study, 70 strains of Gram-positive bacteria and 29 strains of Gram-negative bacteria were isolated. Another 1 strain of Streptococcus pneumoniae was not obtained in culture due to the phenomenon of autolysis. In general, the percentage of successful accelerated identification for all groups of bacteria was 86.0%, and for gram-negative rods it reached 100%, for gram-positive cocci – 83.5%.

Conclusions.

The use of methods for accelerated identification of positive blood cultures with MALDI-TOF MS allows faster and reliable detection of pathogens of gram-negative bacteremia. The effectiveness of detection of gram-positive cocci is reduced to 83.5%.

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